struct NoImpl {
    // This is a defining declaration for the copy constructor,
    // so there is no implicitly defined copy constructor.
    NoImpl(const NoImpl& x, int i=0){}                       // 'Implicit Constructor Shadowing' warning issued here
};

struct ImplShadowed {
    // There IS an implicitly defined copy constructor for this class,
    // because this declaration does not indicate the defaulted parameter.
    ImplShadowed(const ImplShadowed& x, int i);
};

// Definition matches signature of copy constructor, even though declaration doesn't.
// (parse error)
ImplShadowed::ImplShadowed(const ImplShadowed& x, int i=0){} // 'Implicit Constructor Shadowing' warning issued here

struct ImplOk {
    // There IS an implicitly defined copy constructor for this class,
    // but it is not shadowed by the definition of this constructor.
    ImplOk(const ImplOk& x, int i);                                    // Ok: no user confusion or parse issues. 
};

// Constructor definition does not have type signature matching that of the copy constructor.
ImplOk::ImplOk(const ImplOk& x, int i){}  

void my_init(NoImpl x, ImplShadowed y, ImplOk z){
    // Calls the explicitly declared/defined copy constructor.
    // This may not be what a human reader expects.
    auto ni_copy = NoImpl(x);            

    // Resolution conflict: matches both implicitly defined copy constructor and explicit definition.
    // (parse error)
    auto ishadow_copy = ImplShadowed(y);  

    // Calls the implicitly declared/defined copy constructor.
    auto iok_copy = ImplOk(z);            
}